Sleep advice for families is an industry, and it is not what this article is. There is no routine here, no schedule and no method. What follows is an attempt to describe what sleep appears to be doing to recently learned material, because it is genuinely interesting and because it is almost never separated from the instructions.
Sleep is not the brain switched off
The old picture had sleep as a rest period. That picture is not survivable given the evidence.
Sleep has structure. It cycles through stages with quite different electrical signatures, and the proportions shift across the night, with more deep slow wave sleep early and more rapid eye movement sleep later. It also changes profoundly across development: infants spend far more of their sleep in the rapid eye movement stage than adults do, and the architecture reorganises through childhood.
That is a lot of organisation for a system doing nothing.
Consolidation, and what the experiments look like
The core experimental design is simple and has been run many times in many forms. Teach somebody something. Then either let them sleep or keep them awake for an equivalent interval. Test them.
Across many task types, retention is better after sleep than after an equivalent period of wake. This holds when time of day is controlled and when the interval is matched, which rules out the simplest alternative explanations.
More striking is that some effects go beyond retention. On tasks with an underlying regularity that participants have not consciously noticed, performance after sleep sometimes shows evidence of the regularity having been extracted. Something is being reorganised, not merely preserved.
Work in animals has found that patterns of neural activity recorded during a learning task are replayed during subsequent sleep, in compressed form. That is about as direct a piece of evidence for an active process as this area offers.
Why generalisation is the interesting part
For a magazine about how children learn, extraction of regularities is the finding that matters most.
Much of early learning is exactly this: encountering many instances and coming out with a rule nobody stated. Grammar works this way. So does much of early number and reading. The child is not told the pattern; the pattern precipitates out of the examples.
If sleep contributes to that precipitation, then a substantial part of what looks like overnight progress may be literally overnight. Parents report this constantly: the thing that was impossible on Tuesday is straightforward on Wednesday, with no practice in between. The anecdote is not evidence, but it is at least consistent with a real mechanism rather than with wishful thinking.
Naps in early childhood
Young children sleep in more than one block, and the daytime portion is not merely a shorter night.
Experiments using the same teach, delay, test structure with preschool children have found benefits of a nap over an equivalent period of wake on some memory tasks. This is one of the better designed corners of the area, because a nap allows a controlled comparison within a single day.
What it does not license is a rule about when children should stop napping. The transition out of daytime sleep happens across a wide age range, varies between children, and is not something a magazine should be legislating.
School start times, and the adolescent shift
Slightly outside our usual age range, but it illustrates the physiology well. Adolescence involves a documented shift in circadian timing: the biological signal for sleep arrives later. This is a change in the clock, not a change in willingness.
The obvious inference, that school start times should shift, has been tested in a number of places with mixed and generally modest results. It is a good example of a well established physiological finding whose policy consequences turn out to be complicated, which is a pattern we describe in what one study can tell you.
On the figures for how much sleep a child needs
Published guidance gives ranges by age, and those ranges are useful as descriptions of populations. They are less useful as targets for one child, for the same reason all population figures are, which we set out in the range of normal.
Individual sleep need varies. Two children of the same age can differ substantially and both be entirely fine. The information available at home, whether the child is rested, well, and functioning, is better evidence about that child than any table.
Where sleep is a persistent difficulty for a family, that is a reasonable thing to raise at a health visitor review or with a GP, and the NHS publishes general information. This magazine does not give sleep advice and will not start.
The point of describing it this way
Almost everything written about children and sleep is instruction. Instruction implies that the parent is the variable, and that the outcome is under their control, which is a heavy thing to hand somebody at four in the morning.
Described as physiology, it is a process a body performs. It is interesting in the way digestion is interesting, and it is not a performance being assessed. That framing is not a technique either. It is just a more accurate description of what is happening, and accuracy tends to be less punishing than the alternative.